Of the Box

New Graphene Device Can Turn Polluted Seawater Into Clean Drinking Water In One Go

A newly invented variant of graphene has successfully been used to make the heavily polluted water in Sydney Harbor drinkable. Dubbed GraphAir, its inventors explain in an accompanying press release how their “perfect” water purification membrane is able to filter out essentially all the dangerous contaminants and salt in one single go.

Publishing their work in the journal Nature Communications, the team – led by the Commonwealth Scientific and Industrial Research Organization (CSIRO) – note that their tiny, proof-of-concept “supercharged” purification device can process around half a liter (0.11 gallons) of water per day.

That’s not much in practical terms, but if the membrane is as successful at clearing up water as this work suggests, it’s just a question of scale at this point. Besides, its applicability to parts of the world that are still scrambling for easily accessible, clean drinking water is immediately obvious.

“Almost a third of the world’s population, some 2.1 billion people, don’t have clean and safe drinking water,” lead author, CSIRO scientist Dr Dong Han Seo, said in a statement.

He’s not wrong. Water contamination is a ubiquitous problem, one that crops up in the wealthiest of nations – lest we forget the lead-spiked water running through Flint, Michigan – as well throughout much of the developing world. In fact, a recent study noted that pollution leads to 9 million premature deaths every single year, and although air pollution is primarily responsible, water pollution comes in a close second.

Water filtration technology, therefore, is a top priority, so it’s no surprise that engineers have turned to graphene.

Conductive, atomically thin, ultra-strong, and extremely light, graphene is multifunctional; as a result, it’s been used in various endeavors, from futuristic prosthetics with graphene-powered artificial skin to enhanced, durable tennis rackets you can buy today.

Water filtration devices have also been trialed, and although several have hinted at success, one key issue with them is that graphene is still very expensive to manufacture. Few processes are available to cut down the costs in this regard, but last year, as also elucidated in a Nature Communications study, they struck gold.

As the name suggests, GraphAir isn’t manufactured in the conventional way, using high temperatures, high pressures, and long timescales. Instead, the researchers managed to find a way to make it using the humble soybean. Specifically, soybean oil: when heated, it disseminates into carbon units that can form single-to-multilayer graphene film in just a single step.

Using ambient air – hence the name – this process means graphene can be produced very cheaply, so that’s that problem solved. As a bonus, a variety of similar materials, including oil left over from barbeques, works just as well as soybean gloop, which means this mechanism is also relatively eco-friendly.

Graphene, frustratingly, is hydrophobic, which means it normally repels water. In order to circumvent this problem, the team added some microscopic channels, which allowed the water to pass through, but which prevented pollutants and salt, which are far larger molecules, from going with it.

Alone, a typical water filtration mechanism gets clogged up by these pollutants over time, and requires cleaning, and often a more complex, pricier device that segregates two types of filters. When overlaid with a GraphAir filter, however, the team found that not only were 99 percent of contaminants filtered out at twice the rate of the ordinary filter alone, but clogging never became an issue.

So, although it’s early days, the team have essentially concocted a cheap, effective, simple water filtration design. We doubt those 2.1 billion people would be disinterested in this kind of success.